Stock exchange monitors referred Pequot Capital Management to the Securities and Exchange Commission for possible securities violations, including insider trading, at least 45 times between 2005 and this year, the commission has revealed in a letter to the US Congress.

The SEC is probing allegations that Arthur Samberg, the hedge fund’s chairman, received privileged information from a Microsoft employee in 2001 and used it to generate profits of $14m. The SEC has not filed any charges against anyone in the case.